The present invention relates to an X-ray radiographic apparatus, a method of measuring head tilt in taking a radiograph, a stand for X-ray radiographic apparatus, a chair for X-ray radiographic apparatus and a head tilt setting device which are suitable, for example, for applying in taking a cephalometric radiograph by a cephalometric X-ray radiographic apparatus.
In an orthodontic treatment, etc., when deciding a treatment plan, generally, taking a cephalometric radiograph (cephalogram) of a patient, and based on the cephalometric radiograph, the cephalometric analysis is performed (for example, see Non-Patent Literatures 1 and 2). Conventionally, as a cephalometric radiograph, a lateral (side surface) cephalometric radiograph is solely taken. As necessary, there is a case where a posteroanterior (PA) cephalometric radiograph is taken, but it is quite rare, even more, the fact is that it is hard to say that effective information useful for the treatment can be obtained from the posteroanterior cephalometric radiograph. The main reason is that setting the tilt in the front-rear direction of the head when taking a posteroanterior cephalometric radiograph is quite difficult, and therefore, every time taking a posteroanterior cephalometric radiograph, the head tilt becomes different. When taking a cephalometric radiograph under the different head tilt, the posteroanterior cephalometric radiograph to be obtained gives completely different impression. For this, under the present conditions, in the first place, the posteroanterior cephalometric radiograph is considered not to be reliable materials in judging the head skeleton, etc. of a patient.
Conventionally, a lateral cephalometric radiograph is said to be taken at the position that the Frankfort plane of the head of a patient becomes parallel to the floor surface (see Non-Patent Literatures 1 and 2). Here, the Frankfort plane is a plane connecting an orbitale with a porion. In order to make the Frankfort plane of the head parallel to the floor surface when taking a lateral cephalometric radiograph, it is known that an infraorbital point pointing bar with a needle-like sharp tip is provided in the horizontal plane in a cephalometric X-ray radiographic apparatus so as to face the face of a patient (see Non-Patent Literature 2). And it is also known that a posteroanterior cephalometric radiograph is similarly taken at the position that the Frankfort plane becomes parallel to the floor surface (see Non-Patent Literature 2).
Also, in the text of Proffit with highest standing in the world as a text of orthodontics (see Non-Patent Literature 3), it is indicated that with regard to the cephalometric analysis, “A cephalometric radiograph is to be taken at the natural head position (NFP), from which the physiologically real horizontal plane can be obtained”.